The invention relates to sampling devices for sampling liquid at a selected level below the liquid surface in a well. Where liquids such as water or oil seep into a well from different vertically spaced strata, the liquids usually tend to remain separated, at least in an observation well or in a normally pumped well when the liquid is not being pumped out. Since liquid from one strata might be more desirable than from another, it is necessary to be able to determine the depth at which favorable flow conditions exist. Once found, one may achieve a well providing only desirable liquid by using solid casing in the strata of undesirable liquid and a well screen in the strata of desirable liquid. One type of apparatus for water sampling in a remote location is disclosed in Mogg et al. U.S. Pat. No. 3,930,754. In the latter apparatus a portable cylinder of gas is used and the gas is injected down one tube to a desired level where it displaces water and pumps it to the surface. Although the patented apparatus performs well, it would be desirable to have an even more lightweight, economical and easy to carry device.